On February 5, 2024, the Board of Directors of MKS Instruments, Inc. appointed Michelle M. McCarthy to serve as Vice President and Chief Accounting Officer, effective March 4, 2024. In connection with her appointment, Ms. McCarthy will replace Seth H. Bagshaw, the Executive Vice President, Chief Financial Officer and Treasurer, as the principal accounting officer, effective March 4, 2024. Mr. Bagshaw will continue to serve as the principal financial officer until his previously announced retirement as Executive Vice President, Chief Financial Officer and Treasurer of the Company, effective April 1, 2024.

In addition, as previously announced, Mr. Bagshaw will remain employed in the role of special advisor to the Company until May 1, 2024. Ms. McCarthy, 43, has served as Senior Vice President and Chief Accounting Officer of Mercury Systems, Inc., where she manages Mercury?s global accounting function. She also served as Interim Chief Financial Officer and Treasurer of Mercury from February 2023 to July 2023 and as Vice President and Chief Accounting Officer of Mercury from February 2018 to December 2022.

Ms. McCarthy previously served in various roles at Analog Devices, Inc., including as Corporate Controller from April 2015 to February 2018. Ms. McCarthy holds a B.S. in Accounting from Suffolk University and is a certified public accountant.